A display system for displaying a guidance picture displaying the positional relationship of a target surface and an excavator such as a hydraulic shovel is known. The target surface is a plane selected as a work object from a plurality of design surfaces constituting a design land shape. For example, in the display system disclosed in Japanese Laid-open Patent Application Publication 2001-123476, the relative positional relationship of a bucket and a target surface is calculated based on detection data such as the position and orientation of a bucket of a hydraulic shovel, and the position, gradient, and the like of the target surface. The display system then displays on a monitor a schematic diagram of the bucket and the target surface as seen from the side. At this time, the display system changes the display scale of the image according to the distance between the target surface and the tip of the bucket. Japanese Laid-open Patent Application Publication 2001-123476 also discloses that it is also acceptable to fix the scale of the image to the extent that all of the body and the work machine of the hydraulic shovel and the target surface are included in the same image and display the image on the monitor.